I have set up several groups of contacts some of whom have multiple email addresses (which I set up using the "Add Field > Email" option in the "Edit Contact" page).
The problem is when composing a message I can see no way to ensure that a message is sent to more than one email address belonging to a contact automatically (I can manually by repeatedly entering the contact name and then arrrowing down and selecting each email address separately).
I have also found that if I use a group name then ONLY the first email address per contact is selected and no way around it that I can find